Amorphous Hydrogenated Silicon Nitride Deposited by Mercury Photosensitization Chemical Vapour Deposition for Optoelectronic Applications

Abstract
In this work we focus on the properties of amorphous hydrogenated silicon nitride (a-SiN:H) films deposited by mercury sensitization Photo-Chemical Vapour Deposition (Photo-CVD) utilizing SiH₄ and NH₃ and their suitability for the realization of III-V semiconductor optoelectronic devices (dielectric insulation, protection of reverse junctions, process mask, selective regrowth, antireflection coating). Using proper deposition conditions we have obtained a-SiN:H films with breakdown field of 8.9 MV/cm, good spatial uniformity of the dielectric properties, refractive index of 1.85 at 1535 nm, quasi-stoichiometric composition (Si/N=0.8), energy gap of 4.22 eV and density of 2.51 g/cm³, absence of pores and bubbles. We can reproduce film thickness, refractive index and energy gap within ±3%, ±0.005 and 0.05 eV respectively. SiN/InP structures similar to the actual optoelectronic devices have been employed in order to test mechanical adhesion and thickness of the a-SiN:H film grown on vertical facets. A-SiN:H films deposited in the optimized conditions have been successfully used in the previously mentioned applications.